The invention relates generally to hydraulically damped bearings for supporting a piston engine, for example, and, more particularly, to a hydraulically damped bearing having an improved ability to insulate vibrations emanating from the engine when the idling speed of the engine is reached.
A hydraulically damped bearing for a piston engine having a liquid-filled working chamber defined by a journal bearing, a bearing member, and a rubber-elastic spring element connected therebetween is disclosed in DE-OS 36 19 685. A compensating chamber bounded by a flexible inner wall communicates with the working chamber by means of a duct-type conduit. The conduit and the expanding elasticity of the spring element cooperate with each other such that when vibrations of an arbitrarily specified frequency are introduced into the bearing member, the liquid volume in the conduit attains a resonant movement. The effective length of the conduit can be shortened by a selectively operable relief valve mounted in the inner side wall of the conduit between the ends of the conduit, which communicate with the working and compensating chambers, respectively. The effective length of the conduit is arbitrarily increased and decreased by activating the valve to attain a damping effect based on resonant effects in the widest possible frequency range. The ability of this type of bearing to insulate vibrations that occur at the idling speed of the piston engine supported thereby is less than satisfactory as such vibrations become noticeable in the automobile body.
Thus, one of the problems to which the invention is directed is to further develop a bearing of the general type discussed above to effectively damp the low-frequency vibrations occurring when a motor vehicle containing an engine supported by the bearing travels over a road and to efficiently insulate vibrations emanating from the piston engine when the idling speed thereof is reached.